Process for preparing filaments from dispersions containing graft polymers obtained from ethylenically unsaturated monomers



United States Patent PROCESS FOR PREPARING FILAMENTS FROM DISPERSIONS CONTAINING GRAFT POLYMERS OBTAINED FROM ETHYLENICALLY' UNSATU- RATED MONOMERS Duane LuGreen, Potsdam, .N. Y1, a'ssignor ME; I; du

P0111118 Nemours and Company, Wilmington, DeL, a"

stage-processes involves t-he-additionof a second monomer at some "stage during the polymerization of a" first monomer-that is, while the'firstmonomer 'is still polymerizing. Polymerization is continued to produce a -copolymer. "It has been noted that copol-ymers'"pre pared in "this manner -have-'properties* which differ "from 4 those of- -'the usual random copolymer prepared a one-stage process which involves adding} all of the monomersto'gether at the beginningofflthe polymerization. In the prior two-stageprocesses a non-uniform productcontaminated with homopolymers of eachof the monomers has usually been obtained.

Accordingly, it is an object' "of this invention to, prepare non-random or graft 'copolymers which are substantially free of any homopolyin'er. Another object of this invention -is the prejap'aration of shaped articles, such as filaments;=fibers, and films, directly fromdhese dispersions without -'melting or dissolv g the polymers -prior-to"extrusion. 7

These objects are accomplished by carrying'outflthe polmerizationunder conditionssuch that astable dispersion is maintained after-addition of'the' finalmonomer. The polymerization oflthesuccessive monomer, such as the second or final monomer, is made to occurionly after: .the polymerization of previously added monomers is substantially complete ;;but while the polyn ie prepared from-the firstjor the previousnronorners isfstill 'polymerizable. A matrix-forming luateri'alg' is added; to the'dispersion. The modified dispersion is extruded into -a setting-medium which gels'or precipitatesfthe'fmatrixz and'immob'ilizes the particles of the' ';g raft copolym er. 'This gelfiber. is then; passed through a regio here it is "subjected to conditions .suitable flfor coales ngl the 'polymer" constituent 'whi'ch is "to contribute most: "to the tensile properties of the: final shaped ar ticle;

The invention can be readily understoodby reference to the'following examples. These 'examplesserve merely to illustratei'the invention, and are not intendedfto; limit 'itin' any'manner. Unless otherwise specified, all' pr'ocesses are carried out at room temperature (appioximately 25 C.) andalI parts-and percentagesare by ei A e t e o q mer :.:t ,i ;;i n- .vtionz have properties-which; areqquite distinct from those of. a. random :c opolymert'of the vsame composition; The

. .methodtwhich is used for preparing the bonded a s polymers of this-invention :has led 10,-} a different; system for designating thesecopolymers; to indicate their gnique preparation and properties. The first and second monomer Lcon ipositionsv .are written in that 3 order withgan arrow. placed betweenv them -tpointing f component back toward the 1 first, ,showing hat; the; secondrcomponent has,been graftdonto-Abe first. The composition of. the graftacopolyrner; is; given in; parenthesis Jafter the second.- coustituenL-the :.-vyeigh t pencentage of each composition. beingadesignated and. separated-by;

at s; ec

a colon. If eitherior both 50f the-gran icopolymer-icoifi-j ponents'is a copolymer, thisis indicatedgbymam both, mail, of the componentsflandseparating; m

bya diagonal line. a The weight ratio otithe 'componentss in this copolymerare indicated byianumei'iml wpreflx given i-intthe "same order and the numbers'iate'ialso arated by adiagonal-line; Fiber stick .temperaturexis also referred Wain amples. This is the itemperature' atwhich 10 will just'stick to "a-aheated' brassablock'after itahas heen pressed against the block tforlfivelsecondsi with 'gram weight.

' I Example I -to a three-neckedfiaslc equipped yv'itha s and nitrogen inlet tube. Thefiaskwas gen, and".0.4 part ,of ammoniuripers il Lo sad sm t b lfi' t r t 1,4 9?- l ture washeated to 40 CL-[and f ,was added to the well' sti'rred sollit o th ac t apn a-a t .of about "5.5 hours, '50 th ad an lpv y' sl'i sfl d tiona m-salmo- .4 91 i Oflthe? 1 coagulated-, filtered, washedland dried. Th ,mer' had the followingiptqpetfie'sz m: dim fl y i mami fl aim. moist ure =0,3 2 3 v From the nitrogen anal 'ysis',it was ,calculated rq yms was i qr vs t faa T of 39% @Pdof-jac'r onitrile to portion of thepol V and .extr actedfwi E mpl 11- A s a m w yn ep sdr d er i n-1 ffit ib z' w t ll W lutio -9 :sqdi mlals aa throughjia sand packland e tti'uded hole spinneret m'd'er. a pressure of spin was extruded into a 2% "sol x thio'cyanate. precipitated thel so calcium alginat e, which served" ask-the. ,fiber. The: gel: fiber was ,then .,dragg5 .a bath containing.,a 5 6 aqueous al l' in' Iass i i st ia iilsi it This was passedinto' a bath of ic ,ed.

These,filaments werethen drawn14x ans C. After Eiample 1,11"; 11,1." One hundred-sixtypartsof water"'anditwo"'partsf of 2 11 m r6 .-.we cha ged-:31 to-s azthreesneckedlflash Patented June 24; 8

equipped with .a stirrer, condenser, and. nitrogen .inlet tube. The flask was purged with nitrogen, and 0.2 part of ammonium persulfate ahd 0.1 part of sodium metabisulfite wasaddedi 't'Ihe mixture wasthe ated toAO? C. Fifteen parts of vinyl acetate was added to the well-stirred solution and.polymerized to apparent completion in 2.75 hdurslatMO Fifteen parts: offacrylonitrile; was then i g 'dipolymerizationi continued atithesarne temperafor 3.25'= hours. Measurement 'of theisolids .con-

tent. of an aliquot of the stableidispersion obtained indicatod that overall tconversion eto,polymer .was esaiiitially quantitativesi i After. .being precipitated, washed and dried, the polymer :was i found .to i be insoluble in ace-. 5

aqueous (solution of" calcium thiocyanate. After one foot otitravelin this bath the gel filament was transa 56% aqueous. solution ofcalcinm thiocyanate a y M B gfoot dftiaYelip thisfbath'the filament was rwoimd at126' per-minute. filament was subsequentlj'drawn at 165 C.tofourteentimesitsoriginal The drawn fiberhad the following properties:

i a I #73:] grams perfdenier and denier= 3.5. Thefil anientsprepared from the" graft copolymer' were I found tohavea fibersticktemperature of 166 C. Filal niehtsjarepared iii the samemanner 'from ai 50:5 0.mix-

to have a fiber stick temperature of 195 C. A filament prepared under similar conditions from a 30:70 mechanical mixture of polyvinyl acetate and polyacrylonitrile was found to have a .fiber stick temperature of 160 C.

Example 1 A polyvinyl acetate polyacrylonitrile copolymer containing 45% vinyl acetate and 55% acrylonitrile was prepared in a manner. similar to that described in Examples I and III. The polymer had an inherent viscosity in dimethylformamide of 4.2 and was insoluble -inacetone. The stable dispersion of] copolymer which was obtained contained about solids.

Fifty ml. of this dispersion was mixed with 50 ml. of a l. 1% solut on o i d ni t h mo fie di p j qn was fil r dthr u a. a d p a de t u i qm an d mil onefhole'spinneretunder a pressure of 7 p. s.;i. In one experimentthe. dispersionwas extruded intoa coagulating bath containing 2% aqueous, calcium thioa cyanate, fAfter o ne footgof t'ravel inlthis bath the gel fiberwas transferred to a coalescing bath containing 56% aqueous calcium thiocyanate heated to 90 C. After threefee Of Kaye l in this bath the coalesced fiber was washed in ice water and wound up at 12 per. minute. The filament s werepartially dried and drawn; 10X at 150 C. vThe drawn filaments were found to ha ve shrunk j 11% after being immersed for five minutes in boiling entwas'earriedfinto 'a'n ice'fwater washbath.1,.

68' grams f'per" denier"; jelbngation"=10.2%;

water. After being boiled oil and conditioned the filaments hadthefollowing properties: tenacity=32 grams per denier, elongation 1 9%, initial modulus-:40 grams per denier and denier; 5.4.. a y

Q In a separate experiment thematrix wasformed as before, but the polymer. particles were coalesced in dimethylformamideheated to 90 C. These filaments were washed partially dried and drawn 10X by passing over a bar he ated to 165 C. The drawn yarn shrank about a 5%. after b eing immersed in boiling water for fiveminutes. After boil-off the yarn was dried and conditioned and iound to have the following properties: tenacity: 3.0 grams per denier, elongation 17 initial modulus= 4j7 grams per denier and denier=7.

- ture'ofpolyvinylacetate aiidfpolyacrylonitrile were found,

' t o jhave fiber 'stick'temperjature's 'of only 94 C.

. A .vinyl acetate acrylonitrilegraft 'copolymer was ExamplaVII huiidred parts of water, 0.75 part of sodium "L'orolsulfate. and'0.75 part of Plur0nic F-68 were charged? to the reactor. The reactor was purged with prepared in a:manner similar to that described in Ex-.

amples l and III. The final polymer contained 30% polyvinyl acetate and-7075fpolyacrylonitrile bound to- ?gether. The disjpe'rsionwas concentrated andmixed with an-iequalfvolume ot"a"1%' solution 'of sodium alginate.

This; modified idispersion wasfiltered through a sand extruded through n .008'1 one-hole spinneret pressure of o p. s. i- "The matrix was formed {in a '%jaqueous.solutionlof calciumthiocyanatep After one dot of trayel through this bath"tlie"polyme;r parg the gelifiberwere coalesced ina156'% aqueous 'solutiqn'o fcaloiumthiocyanate heated to 90 C. Coa- "complete'after three feet of tr'avelin this ced filament was washed bypassing a n iiicewater'. f lt was wound up a'tffive r'ym n e- Ti f tabul The properties' at various draw ratios Tenacity Elongation Initlal (g./d.) (percent) Modulus Denier tFilamentsrpr'epared: from' this eopolyiner' were found partially driedfilanientsiwere "drawn'over a bar I nitrogen, andYOJO part-of ammonium persulfate andQlOS parrot sodiummetabisulfite wereadded. This mixture was heated toj40 1C. and 20 parts of betamethoxyethyl I acrylatefwas added. One hour later 30 partsof acrylo- U nitrile added; ,Heating was discontinued after. ap- 7 proximately, two more hours andfthe polymer dispersion filtered." Thefiltrate containedapproximately 20% solids.

"Aportioirof the polymer was isolated, washed, and

dried. Analysis of this polymer showed a moisture content of 0.29% andfa nitrogen content of; 14.81%. The

other. 60

polymer contained 40% :poly" (beta-methoxyethyl'acrylate) and,60%.polyacrylonitrile bonded directly to each Example V1 11 of the filtered'dispersion trorn Example VII "was mixed-with 50 ml. or a1% aqueous solution of sodiumalginate. Tl1e 'modified dispersion; was. filtered through a sand pack and extruded; through a 4 mil, onehole spinneret under a pressure of p 'p; s. i. 'The sodium alignate in the extruded dispersion was coagulated in a 2% aqueous solution of calcium thiocyanate; After one foot oi. travel through this bath the gel fiber was conducted over a weir intoa bath co'ntaini'ng a 56%. aqueous solutionof;calcium thiocyanatehatedto 90 C., which coalesced the'polymer particles. After traveling for three feet throughthis bath; thecoalesced filament was washed iniee waterandwoundon abobbin at a rate of 18. per

Qmiiiutef: T The "partially dried filaments were drawn to approximately-ten times their original length over a bar Example IX Four hundred parts of water, 1.5 parts of sodium Lorol sulfate, and 1.5 parts vof Pluronic F-68 were chargedto the reactor. The reactor was purged with nitrogen, and 0.2 part of ammonium persulfate and 0.1 part of sodium metabisulfite were added. This mixture was heated to 40 C. with stirring. An 80/20' copolymer was prepared by adding 40 parts of beta-methoxyethyl acrylate and parts of acrylonitrile and polymerizing at 40 C. Polymerization was found to be ready for the second component in two hours and after that time fifty parts of acrylonitrile was added and polymerizationwas continued for approximately two more hours at 40 C. Overall conversion to polymer was found to be about 93%. The graft copolymer wasfound to be 'swollenby, but insoluble in, acetone and dimethylformamide. Analysis of the isolated polymer showed a moisture content of 0.24% and a nitrogen content of 15.02%.

Example X One hundred ml. of the dispersion of the 80/20 betamethoxyethyl acrylate/acrylonitrile acrylonitrile (50:50)

graft copolymer from Example IX was mixed with 100 ml. of a 1% solution of sodium alignate. The modified dispersion was filtered through a sand pack and extrudedunder a pressure of 6.5 p. s. i. through a spinneret containing five 0.008" holes. The sodium alginate was coagulated afterone foot of travel through a bath containing 2% calcium thiocyanate. The gel fiber was transferred to a 56% aqueous solution ofcalcium thiocyanate heated to 90 C. This coalesced the polymer particles in the separate filaments. After three feet of travel through this bath, the fiber was washed in ice water and wound up at aproximately eight yards per minute.

Yarn drawn approximately 9 X over, a bar heated to- 165 C. had a tenacity of 2.5 grams per denier.

Example XI TWo hundredparts of water and two parts of sodium Lorol sulfate were charged to the reactor. The reactor 1 was purged with nitrogen, and 0.10 part of ammonium persulfate and 0.05 part of sodium metabisulfite were added. This mixture was heated to 40 C., and40 parts of acrylonitrile was charged to the well-stirred solution.

Polymerization of the acrylonitrile was complete at the end of 6 hours. Ten parts of ethylene bis-methacrylate was added to the dispersion. Polymerization was continued for another 14.5 hours at 40 C. At the end of that time all of the ethylene bis-methacrylate had polymerized and a stable dispersion containing approximately 20% solids was obtained. The isolated copolymer was swollen by dimethylformamide but was not soluble in it.

Example XII Seventy-ml. of the dispersion of the acrylonitrile -ethylaone-hole spinneret into a 2% solution of calcium thiocyanate. After one foot of travel through this bath, the gel fiber was transferred to a bath containing a 56% solution of calcium thiocyanate heated to 110 C. After five feet of travel through this bath, the polymer particles hadcoalesced to form a continuous filament.v This fila-.

This represents excellent form stability for an m s. w sh d, in e w terandwo nd p at a rate. of

y rd pc minu e.-

par a ly. dried yarn; was drawn over, abar he t to about 165 C. toapproxirnately 1.2times its original length. Even higher draw ratios were obtainable. This following properties were measured: tenacity.=5.1 grams per denier, elongation=20%, initialmodulus=36 grams per denied, denier=14 and fiber stick temperature=2l9 Example XIII One hundredtwenty parts :of water and four parts of sodium Lorol??:sulfate were-charged: to a reactor: "The system'was purged withnitrogen, and 0.10 part'of ammonium persnlfate and 0.05ipartof sodium metabisulfite were. added; Thismixture was heated 'to 40;5' C. and 10 parts of'vinylidene chloride and five partsof acrylonitrile were addedto the well-stirred'solution. The C0- polyme-r formed'was. ready for the further polymerization after five hoursat this temperature. A. mixture' 'of '10 parts of vinylidenechloride and 11 parts of acrylonitrile was then added to this'dispersion, and polymerization was continued fors'evenhours at 405 C. Analysis of a portion of the stabledispersion obtained showed that it contained 18.6% solids. The isolated polymerwasfound to contain 36.4% chlorine, which correspondsto an-overall composition of 50% polyvinylidene chloride and 50% polyacrylonitrile.

. Example XIV- A portion ofthe dispersion of the. vinylidene chloride/ copolynger'from Example XIII was mixed'with anequal volume of a 1% solution of sodium alginate; The modified dispersionwas filtered through sand and extruded from a one-hole spinneret into a 2,% solution of calcium thiocyanate. After one foot of travel through this bath, the gel vfiber wastransferred to a bath containing a 56% solution of calcium thiocyanate heated to C. The coalesced filament was washed, in ice water and was subsequently drawn 15 at 121 C.

The drawn filaments were boiled off," dried and-conditioned. The following-properties .were measured: tenacity=3.8 grams. per denier, elongation,=20.%, initial m odulus= 3 6 grams per denier, denier=12.and.fiber stick temperature=183 C. The fiber stick temperature. of-a filament prepared from a random copolymerofthe. same composition is approximate1y 150 C.v

Example XV 14.2 parts of vinylidene chloride was added to the wellstirred solution. Polymerization ofthe vinylidenelchloride. was continued for five hours at 405 C. Atjtheend of,this time 21.2 parts of acrylonitrile was added, and polymerization was continued for two hours at 40.5 C. The polymer isolated from the stable dispersion was found to contain 18.6% chlorine.

Example X VI 7 The, remainder of thedispersion ofthe polyvinylidene chloride -polyacrylonitrile (25:75) graft copolymer of Example XV was mixed with an equal volumeof a 1% solution of sodium alginate. The modifieddispersionwas filtered through sand and extruded from a one-holespinneret intoa 2%. solution of calcium thiocyanate. After one foot of 'travel through this bath, the gel fiber was transferred to a bath containing a 5 6% solution of calcium thiocyanate heated to 102 C. The coalesced filament was paring these results 40-50 c. for four hours.

28 partsrmethyl acrylate.

9 ice water and 'sub s'eciiientlyfdrawn 13.5X

at .165. (3.. The drawn filaments were boiled off, dried al ldiconditioriedi Thefollowing properties were measured: tenacity- 6.2 grams per denier, elongation=18%, iriit ial'imodulus- 5 8 ,grams'per denier and denier: 14. E x arr lple VII The. purpose of this example is to compare a random copoly'mer with a corresponding graft copolymer, specific ally that of Example One hundred sixty parts'of water, 1.5 parts of sodium Lorol sulfate, and 1.5 parts of Pluronic F-68 were charged to a reactor. The system was purged with nitrogen, and 0.2 part of ammonium 'persulfate 'and 0.1 part of sodium metabis'ulfite were added. The mixture was heated to 49.-.C.,.and 20 parts of vinyl acetate was addedto the well-stirred solution. Addition of acrylonitrile was started immediately, so that polymerization of both monomers was occur-ing simultaneously; a total of 20 parts of acrylonitrile was addedduring the course of oriehour. Because of the more rapid polymerization rate of acrylonitrile,.it .was necessary to combine these two :containing a 56% solution of calcium thiocyanate heated to 110 C. l The coalesced filament was washed in ice' water and was subsequently drawn 9X at 93" C. The

V driedand conditioned filaments had a fiber stick temperature of 101 C. The filaments shrank 80% upon being immersed for five minutes in boiling water.. Because 'of this high shrinkage, it, was not possible to measure the tensile properties of the. boiled-off filament. The advantages of this invention are illustrated strikingly by comwith those obtained in Example 11. Example XVIII ,The following ing redients were charged to a reactor: 160 parts water, 0.2 part ammonium perfiuorocaprylate,

0.1 part sodium metabisulfite and 20 parts methyl acrylate.

The reaction mixture was heated to 40 C. and polymerization was continued at that temperature with adequate stirring for three hours. Following this the dispersion 1 was evacuated to remove thelast traces ofunpolymerized shaker tubeand 0.2 part of ammonium persulfate and 0.1 part of sodium metabisulfite were added; The tube was evacuated, flushed with nitrogen, and tetrafiuoroethylene was admitted at 400 p. s. i. The tube was then heated at At the end of this time the pressure had dropped to approximately 200 p. s. i. The residual tetrafluoroethylene was released and the polymer collected. The composition of the polymer was found to be poly(methyl acrylate) polyetrafiuoroethylene (20:80). Tough translucent films could be prepared from this polymer. I Example XIX The following ingredients were charged to a reactor:

. 320 partswater, 3 parts sodium Lorol sulfate, 0.4 part ammonium persulfate, 0.2 part sodium metabisulfite and The reaction mixturewas heated to 40 C. and polymerization continued at that temperature with adequate stirring for2.5 hours. Vinylidene chloride (52 parts) was n the added to thestable dispersion and polymerization con- 'tinuedat'40." Cffor six hours. On the basis of the solids content, theyield of polymer was quantitative.

3 A portion of the polymer was isolated from the disper 'sion, in the usual manner and the following solubility properties observedzlt was soluble in tetramethylurea, dimethylformamide and cyclohexanone and 'insolublein,

but swollen by, dioxan.

The dispersion could be spun directly as was done in the preceding examples, using sodium alignate as the matrix-forming material and tetramethylurea as a coalescing agent.

The term graft copolymer is used in the specification and claims to designate a particular type of ordered copoly rner in which chains of a given polymer composition are attached at various points to a backbone or base chain of adifferent polymer composition. They are usually prepared by carrying out the polymerization in a stepwise fashion. The first monomeric constituent is polymerized to form the backbone or main polymer'chain. After the polymerization of the first monomer is substantially at an end, but while the polymer formed is in the nascent state, the second monomer is added and polymerized. The first polymer is still active, that is polymerizable,,even though all ofthe first monomer has disappeared. When the second monomer composition is added, polymerization is thought to be initiated at active centers remaining in the pre-formed polymer. Thus, the second polymer chain is grafted onto the first; hence the term graft copolymers.

It is not'necessary that either the backbone or the bonded chain be a homopolymer. Either the first, or the second, or both, of the two monomer compositions may be a mixture of monomeric materials, as is shown in the examples. It is also not necessary that this be limited to a two-step process. Theoretically, there is no reason why a third monomeric constituent cannot be added after polymerization of the second is complete. However, from a practical standpoint, this is seldom done because of the experimental ditficulties encountered in attempting to prepare a uniform product.

The time to add the second constituent varies widely, depending upon the nature of the first monomer and the reaction conditions such as temperature and catalyst. Generally, the polymerization of vinyl monomers as described above is substantially complete in about five hours, and the number of active centers remaining decreases quite rapidly after that time. In some cases the optimum times are shorter, being of the order of two or three hours. The times given here are based on polymerizing at temperatures below 50 C. using rcdox catalysts. The active centers are destroyed more rapidly at higher temperatures, and the optimum period for adding succeeding monomers will be proportionally shorter. Any catalyst generally used for vinyl polymerizations, e.. g., redox and, azo catalysts, as, for example, those disclosed in U. S. 2,471,959 and U. S. 2,491,471, may be used in this process. The persulfate-bisulfite system has been found to be particularly effective for preparing the dispersions of this invention.

For monomers which polymerize rapidly, the time at which the succeeding monomer is added is more critical. This is also true for certain catalysts which produce active centers with short lives. Consequently, it is quite difficult to prepare chemically bonded graft copolymers with certain combinations of monomers and catalysts. As has been indicated earlier, this is also true if the first poly- ,merizationis allowed to continue too long. However, using the preferred conditions which have been described, the dispersed polymer particle still serves as the point for initiating the second polymerization since there are so few free micelles left' in which polymerization to prepare homopolymer can start. Under these circumstances there is usually obtained a modified polymer particle in which the second monomer has formed a polymeric coating on the first polymer particle. These coated polymers possess many of the advantages of the prefer d polymers of this invention. However, there are indications that seesaw those of articles preparedbfextr idingdispersions pre- Vessel tinde'i 'con lt ioris', suchfthat giafffcopolym' ntsfornedt i r "Ffo'r'fi'the above examples it can be seen that'a wide variety 'ofiimsaturated ofiipoiunds'niay be used in this invention. T seniclude't o s'efcontaiiiingfvinyl,vinylene n'ylid ne roups as as cbfrb's'pbhding' gronps i'n which haloge torii's' repl e each orsoni'ofthe hydrogen ato s'. "'Onefof-"tlie' most frqiiri'tly used mana ers; is

v oijzitril and, this. rhdnor'nerf may. 'be-used in conjunctio'ir with "such monomers'r'efer edjto,i 'U. '5; Patents Nos, 2,4Q45,7.142,4 04,72,77. ,Useffinlai'rje "si lch monomers, j ,y. n nithyl vinyliketo e, esters oi inet a'rylic and acrylic acids; vinyl halides nd vinylid gl des, such as iyinyl chloride, v ny nuo ride "and"vinyliilemi ch!" butadiene, is'ob'ntylne, the. 3/1 pyridines; actylaihid, K mono-and, disubstitnt ryllic amide s, vifiyl ethers and thelike. Thus monomer'sfc ontaimng more than one ethylene double bond, su'chl as in 4 diyinylbenz ene, 'may be; employed, Cross-linking can 1 be tolerated because thefdispersioh shapingiprocessfdoes not. reqnire gr eat solnbilityi'n the polymers being shaped. Howeven'for the most part linear polymers areprodilced by this .-inyention and such polymers are generally preferred The polymers lqrepar et l by this invention are readily shapedinto filamentsyfilms, ribbons, ,rods', bristles, tubes and: similar articles. v 1 1 The prferriedtcopolymer s are those which are prepared under conditions s nch't hat: {stable dispersion is main t'airied.thtoilghoutthetprocess. In other prds, the first i on omer" composition is dispersedt in thev polymerization medium, which islusua lly aqneous, andapolymerized; under conditions such that a stable emnlsion; or dispersion of the polymeris obtained. whent -polymerization-of;the first monomer is complete :andlhe :polymer is in the nascent state, the second monomepcomposition-is added and, polymerized to, pr odi ce a'stable emulsion ordispersion -of the t copolymer; When preparing-bonded copolymersby this method,- it;is-essential that no emulsifying-fagent or soap.- be added-withthe second monomer composition ifsa true graft copolymer which is freetof homo'polymeris to be obtained. Itiscnstornalry to add' all; of. the, emulsifying-o1"dispersing,agent prior to the first; monomer composition. It'is-also preferredxnot-to add any additionalqcatalyst oractivatoralong w'ith the second monomer composition. Control of, thesezcomponents is not ash critical-as iscontrol of the soapmiclle concentration, but it is desirable to add all ofgthe, catalyst nzingi the Iwo 'rfionemers 'in the, same andactivator prior; toi thevvstart; of the polymerization to V minimize contamination of the copolymer with'homopolymer. i

' Itl-hasybeen recognized: that shaped. articles; such as fibers and films, prepared from'th copolymers of this invention are different fromcomparabl'e shaped articles preparedfrom mixtures'of polymers and -ffc gin "ratid o rn copolymers' of thasqme emmrs; i s'true even when; the shapedjrticles'fl are preparediby processes known to the art.' However, it is impossible to utiliie all of the nniquelpropertiesl of these new copolyrners by use of, the .-usual ,soli1 tidn; orfmelt processes. The

i -RlYthttWfhii eve i t was h thigh/l1 'me r se'd is boiling' -yvateffor Iive me es;

Eleven grams: of the which have been described previousl 1 some processes, 31' Iii this proces 'polyme copolymer and v'y'hich can be pr mam; temperatnr e-"yyater bath: The was then gshrinkage was 8.4%", I" Y a s ri kssew sz j T us h l a e s fs is nten ion has; y; a shrink ge i e sw'ptssq s qiithis. zxcmionip qdsmes..pro uctswhich are"diifere'nt'f oniand up'eriprfto, those y, an better" than s s h co enm'at'rixforming material" is incorporated in jthe h eo dispension-ofi the h Q ei dispq ion'i s shansd yi ek- I L H tojase'ttingmedinmfilflie gel structure obtained on"setting comprises; the substantially immobilized discrete bedded' in the df inat rix mer particles are thse piepa ed froni thefsarne prod];

ftoge'tli -w'it h m1 n 0! q 1l nutiess o forming material; x

The mania-forming material-comprisesja cationic 'or anionic polymeri m o a nu t'ra le polymeric material whifch' s s In in. si'onj of'the graft H v K 1 p1 While, most materials used to form" the (matrix r snppqrting str 'ttcture are 'i'fiber-fo fming,l"iff is not" essential, that they be initially fiber-forming Materials whibh are not of themselves fih'er formingt but" which upon 4 extrusion 7 into a setting medi 1m;are formed rinto fi bergcan b etuse d. '7

Spitable f anionic; polymeric materials contain a plurality of acidic groups, suchas carboxyl, su lfo'nic, and] or 7 As specific examples ma be mentioned; alginates,'. earboxylalkiylf cellnlo ses, carboxymethylhydroxyethyl' celluloses p ectinate s; pectates," polyacrylat es pdlymethacjrj sf Beth-carbonyethylmetha'cryla'te polymer," beta carboxyethylacrylaie polymer, water-soluble modified'styrene polymer resins, partially. hydrolyzed polyac copolymers of forming :material's. contain a plurality of basic groups,

usually amino and/'orxquaterna'r'y: ammonium group's.

Esamplt s oft useful; cationic," polymeri'c electrolytes are diethylaminoethyl methacrylatepolymeml hydi ol'yzed vinyl. pyridinegbl-vinyl r r 1'N'.(2, instituted. amino qu ternaryflammonium be u1y1oxymthy1- ih iq ammetrs .i su name wit titralj i se ataiaiai elii a; t

lulose; cel ulose acetate, cyanoethyl cellulose, polyacryl- .a n t d polyviny alcoho I forming I 'inaterial are T'r'equrred to prov de ac dic advantage; The iquantity used .rang es 'f rom 0.10% 30.10% by cweight of the disperisi 0,25%.to;5% being preferred. The spe- Qcific quantitypreferred. varies the matrix material. ThefmiiiingfoperationfrnayIbe carried out in any one Tet a number; of, .waysl. ,;For instance the fiely divided dry polymerlmay be addedto a solutionofithe; matrixitor'niing material 'or lth e dry polymeric matriigforming material may 1 be. ,added to, an" aqueous dispersion or j emulsionfot the polymer. It, is, also possible that the dryi polymer and dgy matrix#forming material may ,be miired and simultaneously incorporated inan aqueous me i m A Pr er ed. me d, t a a eso in itd ns m t al i hsn'aque us ish met-.1, t dispersio'ns' containing, the, matria forining e "flow'able, especially when the polymer concentrajt on less thangjabout,v 6 t)% ;by weight. Shaped objects are prepared from these dispersions, ,Which prefi'erably contai'nlfrom ;5,,60%.. by weight of the -polymer, by "extruding through a shaped orifice into a precipitating.0!.immobilizing.medium; During this first stage of the fprQcessQBroiwnian' motion, of the polymer particles j practi'cally stops. ai'id Zthe fmatrix forms a gel-like 'structure iwhiC hf 'suppo "the particles The precipitated V f ngth. The .iclioice, of matri oforming material will d end to some. cit tent onlthe dispersed copolymer. It" .is obvious that one willitise. a matrix-forming materialQwhicliiwillfnot' coagulate polymer inthe dispersion.priorto1shaping,, 1 be setting or immbb il'zing mediummay be any fluid of precipitating .Lor' gelling ,the matrix-forming Included are air. and lcornpounds such as volaleiand possesses a fair degree of.

etaem e ulose, hydroxyethyl. celtile istr o g ia ias; and aqueouisg solutions of inorganic "compounds {I ate r-miscible rorganic compounds. 'Preferabl'y, an aqueous solution containing a lowcon- ,c ntrefi n 9 t e.i re pi at ns g nt, emp oye In allf cases, pre tation is pi aetieally instantaneous,the time required be ng: of ,the order of 0.04 second.

Aqueous solutionsbf pblyvalent metal salts are particularly usetul "as 'p'recipitan'ts whengan anionic matrix- I fpijmitig material isused. Solutions containing from0.5 to 4.0% byfweightofthe following. salts are suitable precipitjatingfagents: calcium thiocyana'te, aluminum sulfate, potassium aluminumsulfate, barium thiocyanate; zinc chloride,"magnesium bromide, calcium iodide and chrofmou s nitratel Solu sulfates, 'di andr poly-sulfonic acidsandlheir salts iiiTaqueous;sol1itionare suitable precipitants for use j when thematrix-forming material is a cationic material. The following compositions have. been u sedas setting mediator non-ionic matrix-formingmate'rials; 50%, aque'ou's ammonium sulfate,- 40% aqueous calcium chloride, 30%; I aqueous; aluminum sulfate and 350% aqueous ammonium acetate. Many materialsgsuch as alginic acid,-;are insoluble; in :Water but aresoluble as salts. or ;in bases;v and aqueoussolutionsof acids 'such as hydrochloric, tsulfuricia'nd sulfamic acids can be used as precipitants. Similarly; matrix-forming materials which X are soluble lin, acids but {insoluble in (water, may be pre- Inthe second stageof the process, the substantially immobilized water-insoluble polymerparticles coalesce or flow togetherjwithout destruction of'the formed article. Coalescenceis achieved in various ways, the preferred method for anyone polymer depending upon the polymer itself. The modified polymer dispersion .may'be extruded into a setting medium which will precipitatethe matriX- jforniing materialbut which exerts little or no solubiliz ing action on the polymer particles. Thereafter theshaped structure is exposed to the coalescingaction of an agent which is capable of dissolving the polymer. In most cases this has beenfouncl to be the preferred method of operation. However, it is possible to eXtrude the polymer dispersion into a liquid medium which will precipitate the matrix-forming material and will also exert solvent action on the polymer particles in the p'recipitatedinatriX.

The exposure to this coalescing action of the solvent maybe accomplished by passing the coagulated structore through such a solvent or by air drying the shaped article which has occluded minor amounts of a solvent. In any case, the time of exposure to the solvent action is so regulated that the particles coalesce without destroying the shaped structure.

The polymer particles in the shaped article may be coalesced with the aid of organic liquids or concentrated aqueous, solutions of salts and mineral acids. For a low cost, ease of handling and safety in use, aqueous salt solutions are generally preferred for coalescing. The watersoluble salts used for preparing the solutions are preferably metal salts of inorganic acids. The salts should be sufiicicntly soluble in water to yield 10% solutions, and preferably, at least 30% solutions. Furthermore, concentrated aqueous solutions of the salt being usedshould be capable of dissolving thepolymer component being coalesced at some temperature up to the boiling point of the salt solution.

Organic compounds which are to be used as coalescing agents should, preferably, be capable of dissolving the polymer constituent at temperatures below their boiling points. However temperatures higher than the boiling pointof the liquid maybe used by conducting the process in the vapor phase or under pressure. "Organic compounds suitable for coalescing polymers include'dimethylformamide, dimethylacetamide, m-cresol, methyl 1 ethyl ketone, tetramethylurea, adiponitrile, cyclohexanone, acetophenone andmesityl oxide.

Certain salt solutions have a specific solubilizing action on some polymers and'will coalesce the bonded copoIy- -mers containing a sufficiently high percentage of these constituents. For example,,salts which are highly useful in coalescing acrylonitrile graft copolymers include the following: lithium thiocyanate, lithium iodide; lithium bromide, sodium thiocyanate, sodium iodide, potassium thiocyanate, magnesium thiocyanate, calcium thiocyanate, calcium iodide, calcium bromide, manganese thiocyanate, zinc thiocyanate,'cadmium iodide, and the chlorides bromides, and iodides of zinc, tin, iron and cobalt. Suitable organic liquids include dimethylformamide, m-cresol, xylene, methyl ethyl ketone, tetramethylurea and adiponitrile. In coalescing the polymer particles, room temperatures or lower can be used, but it is generally preferred that the coalescing bath be heated, since less time is needed.

Removal of the coalescing agent from the shaped polymer. is readily effected by washing. ln washingmultifilaments, it is generally preferred that cold water be .used. The resulting structure may then beQafter-treatedwith boiling water and, if desired, stretched to orient the molecules to elfect improvement in physical properties. On

the other hand, the coalesced structure may be partially or c om pletely oriented by. drawing prior to the washing p; 'f Q i p, In-additionto water, matrix-formingmaterial andpolyliner, the dispersion used for producing the shaped articles can contain iiispersingagents, plasticizersjpig'ment's, dyes,

13 clay, silica, alcohol, acetone and similar materials. Alternatively, these materials may be incorporated in the coagulating bath, in the coalesc ng bath or in separate baths or a combination of these. These substances may or may not appear in the final shaped articles. If desired, the coagulated articles may be passed through'a bath between the coagulating and coalescing media for Washing, filling, plasticization and the like prior to coalescing.

The shaping process of this invention can, of course, also be applied readily to graft copolymers prepared by previously known methods. Regardless of the source of graft copolymer, it is possible to prepare by this method shaped articles with unique properties. A particular advantage is realized when utilizing the previously described, preferred graft copolymers, i. e., those prepared under conditions Where a stable dispersion is maintained throughout the process and where no soap is added along with the second monomer composition. The polymer which is being coalesced may be' present as the first or second component of the graft copolymer, or it may be present in both components. For generally simpler operations it is preferred that the polymer which is being coalesced be present in the second component of the graft copolymer. In order to obtain a shaped structure having tensile properties approximating those of a shaped structure prepared in a similar manner from the homopolymer of the constituent being coalesced, it is required that either the first or the second component contain at least 40% of the polymer for which the coalescing agent has been selected. For practical reasons it is preferred that the graft copolymer has no more than four monomeric constituents and that the constituent which is to govern the tensile properties of the ultimate shaped structure comprise a least 40% of the total weight of the monomers.

The graft copolymers which contain acrylonitrile are a preferred species of this invention. Of these copolymers those which contain at least 60% by weight polyacrylonitrile are preferred, since they possess tensile properties which are substantially equivalent to those of an acrylonitrile homopolymer prepared and processed in a similar 'manner. The added constituents are selected and combined to obtain the desired modification in properties other than tensile properties. For example, the dyeability, drawability, glazing temperature, fiber stick temperature, flammability, hydrophilicity and many other properties can be modified while still retaining substantially all of the desirable tensile properties of acrylonitrile homopolymers. Shaped articles prepared from graft copolymers by this process possess a combination of properties which cannot be obtained in any other way. For example control of the elasticity and tackiness of articles prepared from synthetic elastomer compositions is possible. As a specified example of this type of application, a graft copolymer was formed in which the first component was a 70/30 copolymer of chloroprene and acrylonitrile, and the second component waspolyacrylonitrile. The film prepared from this dispersion was clear and elastic but not tacky. Also, it was found that the abrasion resistance of fibers prepared from acrylonitrile polymers would be improved .by use of graft copolymers in which the first component was polyacrylonitrile and the second component was a softer polymer, such as poly(ethyl acrylate) and poly(vinyl acetate).

Another particular advantage of this process is that polymers of high molecular weight maybe readily utilized. The preparation of filaments from solutions of the high molecular weight copolymers generally obtained in this process would be impractical because solutions" containing commercially useful concentrations of polymer have viscosities which are too high to be processed under reasonable conditions. However, in the process of this invention the viscosity of the dispersions is independent of the molecular weight, so that there is no upper limit to the molecular weight of the polymers which can be utilized.

' The dispersions can be, and preferably are, quite concentrated with respect to the amount of polymer present. A further advantage of the process is that isolation of the polymer is not required, since they are prepared and utilized in the form of aqueous dispersion-s. Finally, the temperatures employed in this process are generally low, in the vicinity of room temperature, and, if high temperatures are needed, only short exposure periods are required. As a result, the products are not discolored during formation and are essentially white.

Any departure from the above description which conforms to the present invention is intended to be included within the scope of the claims.

I claim:

1. The process of preparing filaments which comprises forming a dispersion of a polymer in particulate form by polymerizing an ethylenically unsaturated monomer in an aqueous medium, adding to the said dispersion after polymerization of the monomer is substantially complete but while the resultant polymer is still in the nascent state, a second ethylenically unsaturated monomer to obtain a particulate dispersion of a copolymer of the two said monomers, adding to the resultant dispersion a settable matrix-forming material which is soluble in the said dispersion, extruding the dispersion through a spinneret into a medium which precipitates the said matrix-forming material by rendering it insoluble, and thereafter coalescing the particles of the copolymer embedded in the matrix-forming material by contacting the same with a fluid which has a solvent action on the copolymer particles.

i 2. The process of claim 1 in which the copolymer has an acrylonitrile content of at least 60% by weight.

3. The process of claim 1 in which the second monomer is added without the addition of further emulsify- 7 ing agent. 7 p

4. The process of claim 1 in which the said fluid is a liquid.

5. The process of claim 1 in which the matrix-forming material is added in the amount of from about 0.10% to about 10% by weight of the dispersion.

6. The process of claim 5 in which the percentage is from about 0.25% to about 5%.

7. The process of claim 5 in which thedispersion contains from about 5% to about 60% by weight ofthe said copolymer.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,840,44'7 June 24, 1958 Duane L], Green It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

001111111174, line 66, for "p pd. s, in" read 6 pa, 5,, in column *7, line 52, after "unpolymerized" insert F monomer, The polymer dispersion was transferred to a polymerization line '73,- for "the"; first occurrence, read then .m; column 9 line 27, after i'luoricle insert we vinylidene A Signed and sealed this 2nd day of September 1958.

A??? KARL H mm: ROBERT (J. WATSON Attesting Oflicer' Commissioner of Patents 

1. THE PROCESS OF PREPARING FILAMENTS WHICH COMPRISES FORMING A DISPERSION OF A POLYMER IN PARTICULATE FORM BY POLYMERIZING AN ETHYLENICALLY UNSATURATED MONOMER IN AN AQUEOUS MEDIUM, ADDING TO THE SAID DISPERSION AFTER POLYMERIZATION OF THE MONOMER IS SUBSTANTIALLY COMPLETE BUT WHILE THE RESULTANT POLYMER IS STILL IN THE NASCENT STATE, A SECOND ETHYLENICALLY UNSATURATED MONOMER TO OBTAIN A PARTICULATE DISPERSION OF A COPOLYMER OF THE TWO SAID MONOMERS, ADDING TO THE RESULTANT DISPERSION A SETTABLE MATRIX-FORMING MATERIAL WHICH IS SOLUBLE IN THE SAID DISPERSION, EXTRUDING THE DISPERSION THROUGH A SPINNERET INTO A MEDIUM WHICH PRECIPITATES THE SAID MATRIX-FORMING MATERIAL BY RENDERING IT INSOLUBLE, AND THEREAFTER COALESCING THE PARTICLES OF THE COPOLYMER EMBEDDED IN THE MATRIX-FORMING MATERIAL BY CONTACTING THE SAME WITH A FLUID WHICH HAS A SOLVENT ACTION ON THE COPOLYMER PARTICLES. 